Download EEHV Monitoring and Diagnostic Testing of “At Risk” Juvenile

EEHV Monitoring and Diagnostic Testing of “At Risk” Juvenile Elephants
Routine monitoring of elephant calves for Endotheliotropic Herpesvirus (EEHV) by
quantitative PCR (qPCR) is proven to detect low levels of EEHV in the blood before
clinical signs occur, allowing increased monitoring and early therapeutic intervention if
viral level increases (Stanton et al., 2013). The increased sensitivity of qPCR and multiple
rounds of cPCR and the ability to quantify whole blood viral levels with qPCR allows for
better management of calves with regard to possible EEHV Hemorrhagic Disease (EEHV
HD) development. If qPCR isn’t available, multiple rounds of cPCR can be a sufficient,
but not ideal, replacement. It is now possible to detect and quantify low levels of EEHV
in the blood to distinguish between a calf’s subclinical or non-hemorrhagic herpes
infection and the much more serious EEHV HD and monitor closely for rapid increases in
viral levels. Elephants can have low levels of EEHV in the blood with no or minimal
clinical signs (Stanton et al., 2013) for up to two months, but possibly for as long as one
year.
Trunk wash or saliva screening can also detect shedding of virus (as DNA by PCR)
for several months during convalescence after primary viremic infection or occasionally
from reactivation of a latent infection. While there may be some overlap between high
levels of viremia and shedding, viremia is the only parameter that correlates most
consistently with disease. High levels of EEHV in blood are typically found in cases of
EEVH HD. Screening trunk wash samples for 2-3 months may allow the determination of
the types of EEHV present in the herd, with the caveat that only EEHVs that are being
shed in the trunk secretions during the collection period would be detected.
Standard monitoring and testing protocols for elephant owning institutions should be
developed, to maximize the knowledge gained by appropriate testing while optimizing
the use of resources (time and reagents). This document has been developed as a guide
for the monitoring and testing of any managed elephant; calf training should be a
priority to facilitate this. A similar document is being developed for approval by the
European Elephant TAG.
Routine EDTA whole blood (WB) screening
Recommended testing for calves aged 1-8 years (minimum) or 1-13 years (optimal):
Weekly EDTA WB testing by qPCR (or two rounds of cPCR)
Asian elephants—test for EEHV1 (minimum); add-in EEHV3, 4 and 5 (optimal)
African elephants—EEHV2, 3 and 4 (minimum); add-in EEHV1 and 6 (optimal)
Optional: Bank EDTA WB and serum samples from the rest of the herd weekly for
epidemiological investigation in case of a positive EEHV PCR result or clinical signs in a
member of the herd.
Basic TW screening to determine herd EEHV prevalence
Asians elephants—collect once/week on all herdmates, for a duration of 2 months
(minimum) or 3 months (optimal); test for EEHV1 (minimum); add-in EEHV3- 4, 5
(optimal)
African elephants— collect once/week on all herdmates, for a duration of 2 months
(minimum) or 3 months (optimal); test for EEHV2, 3-4 (minimum); add-in EEHV6
(optimal)
Only EEHVs that are being shed in the trunk secretions during the collection period will
be detected.
If EEHV (+), sequence appropriate genes to determine the subtype.
EDTA WB POSITIVE for an EEHV
IF NO CLINICAL FINDINGS INDICATIVE OF EEHV HD ARE OBSERVED:
Collect EDTA WB samples 2-3 times in the first week and closely monitor the viral levels
provided by the testing laboratory. Consider initiating recommended anti-viral and
supportive therapy based on:
Observation of clinical signs
Viral load of 5,000 viral genome (VGE)/ml or greater
Rapidly increasing VGE/ml
Consult eehvinfo.org and members of the EEHV Advisory Group veterinary subsection
for current treatment recommendations.
Continue collecting samples 1-2 times per week after the first week and use information
on viral load, viral trends and clinical observations to determine if testing frequency can
be reduced. Continue monitoring the viral load until EEHV is undetectable in EDTA WB.
Optional: Bank sera from affected elephants weekly. Continue banking EDTA WB
samples from the rest of herd weekly or according to the institution’s normal husbandry
procedures.
Also see “Clinical Findings in EEHV HD” on the eehvinfo.org website for more
information on what to look for.
IF CLINICAL FINDINGS INDICATIVE OF EEHV HD ARE OBSERVED:
Consult eehvinfo.org and members of the EEHV Advisory Group veterinary subsection
for current treatment recommendations.
In addition to considering treatment of the affected animal:
Immediately submit serum and EDTA WB from affected elephant for EEHV qPCR for
diagnosis and prognosis. Continue testing EDTA WB 1-2 times per week until EEHV is
undetectable.
Collect EDTA WB samples from the rest of herd (twice weekly for calves, once weekly for
adults) for EEHV PCR testing for at least 3-4 weeks; if none are positive for EEHV during
this period, return to weekly testing for the at risk juveniles as above.
Optional: Bank serum from herd.
Reference
STANTON, J.J., ZONG, J.C., ENG, C., HOWARD, L., FLANAGAN, J., STEVENS, M., SCHMITT,
D., WIEDNER, E., GRAHAM, D., JUNGE, R.E., WEBER, M.A., FISCHER, M., MEJIA, A., TAN,
J., LATIMER, E., HERRON, A., HAYWARD, G.S., & LING, P.D. (2013) Kinetics of viral loads
and genotypic analysis of elephant Endotheliotropic herpesvirus-1 infection in captive
Asian elephants (Elephas maximus), Journal of Zoo and Wildlife Medicine 44(1), 42-54